1. Field of the Invention
The invention relates to a polymer modified non-aqueous asphalt composition, a process for the preparation of the polymer modified asphalt composition, and the use of the polymer modified asphalt composition.
2. Description of the Related Art
Asphalt or bitumen (called “asphalt” herein), are terms used to describe the residue left over from the petrochemical refining process. Asphalt is used in a variety of applications, for uses such as, but not limited to, paving, sealing, coating, roofing, waterproofing, and draining, and as weather barriers.
Asphalt without polymer modification is typically soft at room temperature, and tends to be brittle at lower temperatures, therefore lacking properties for use on its own in some of the applications mentioned above. A general strategy is to modify the asphalt with a variety of property enhancing polymers and/or additives.
Polymer modification, depending on the application, is generally intended to provide many benefits, such as, but not limited to, improved viscosity, softening point, ductility, resiliency, tack, flow or creep resistance, adhesion, flexibility, and low and high temperature performance. Most polymer modifications of asphalt in non-aqueous systems are accomplished with styrene butadiene styrene (SBS), styrene butadiene rubber (SBR), styrene ethylene butylene styrene (SEBS), styrene isoprene butadiene styrene (SIBS), styrene isoprene styrene (SIS), called “S-polymers,” herein, and ground tire rubber (GTR) containing the S-polymers mentioned above.
To further enhance the properties of asphalt, a variety of additives have been used. Such additives, include, but are not limited to, extender oils, naphthalenic oils, paraffinic oils, acids such as phosphoric acid, polyphosphoric acid, plastomers, tackifiers, waxes, stabilizers, emulsifiers, rosin esters, fillers and combinations thereof.
During the processing of asphalt, there is a need for processing temperatures well above the melt point of asphalt. Furthermore, the incorporation of certain types of polymers, for example the S-polymers, requires long mixing times for complete and thorough incorporation and homogenization into the non-aqueous asphalt system. The incorporation and homogenization of the S-polymers requires the asphalt-polymer system to be heated to temperatures above the softening point of the S-polymers. Still further, along with the high temperatures, there is a need for high mixing and shear of the system to ensure complete suspension of the S-polymers in the asphalt phase. This processing tends to be tedious and often time consuming, with long cycle times, and may also require long cooling periods for further processing.
Even still further, the S-polymers tend to increase viscosity, reduce tack, and cause excessive heat generation in the mix vessel. Therefore, additives such as extenders, paraffinic and naphthalenic oils, plastomers, waxes, and tackifiers are added to address the challenges of combining these polymers with a non-aqueous asphalt system. S-polymers may be supplied in a variety of forms, for example, but not limited to, blocks, bales, chips, pellets, gratings, liquids, etc., or combinations thereof. Therefore, preliminary processing of some of the forms of the S-polymers is essential. For example, polymer blocks or bales require processing such as crushing, milling, grating, etc., to enable the processes of blending and homogenizing the S-polymers with asphalt to be possible.
EP 0 337 282 B1 describes bituminous materials particularly for the preparation of films, sheets, and roofing membranes, comprising bitumen, polystyrene polybutadiene block (“SBS”) copolymer, and a solid resin of an ethylene/vinyl acetate (“EVA”) copolymer with 40 to 50% by weight of vinyl acetate units. The ratio of SBS copolymer to EVA copolymer is stated to be critical, and must be in the range of 2:1 to 6:1 by weight.
WO 97/44397 A1 discloses bitumen compositions for the use in road applications which comprise a bitumen component and a thermoplastic rubber such as a polystyrene polybutadiene block copolymer, and a solid resin of an ethylene/vinyl acetate (EVA) copolymer with 25 to 35% by weight of vinyl acetate units in the copolymer. With the addition of an ethylene/vinyl acetate copolymer, higher hardness and better solvent resistance is obtained.
WO 2011/112569 A2 teaches the preparation of hot mix asphalt (HMA) which is used as a paving composition. For the production of HMA, aggregate is incorporated into asphalt. In combination with the aggregate, a polymer modified binder (PMB) is added to the asphalt. The PMB is composed of a thermoplastic material (SBS), oil and filler, and it is added in a powder, pellet, chip, flake or granule form.
U.S. 2013/0184389 A1 concerns compositions for pavement with improved resistance against deformation in the summer season and occurrence of cracks in the winter season. The composition comprises petroleum-based process oils, a block copolymer based on polystyrene blocks in combination with polybutadiene blocks or polyisoprene blocks, and a solid resin of an ethylene/vinyl acetate copolymer with a vinyl acetate content of 25 to 45% by weight. For copolymers with more than 45% vinyl acetate, it is reported that there is deterioration of surface properties.
U.S. Pat. No. 4,073,759 describes an aqueous asphalt composition for the protection of metals against corrosion. The composition is obtained by admixing asphalt with SBR rubber latex, polyacrylate dispersion, and a polyamine surface active agent.
It would be desirable to provide asphalt compositions based on non-aqueous asphalt which provide good low and high temperature performance and adhesiveness to substrates, and at the same time, provide for more economic processing.